On robust stabilization synthesis for plants with block structured modeling uncertainty

In this paper we consider the problem of robust stabilization of plants with additive block-structured uncertainty. This problem reduces to an optimization problem of the form ??-1,??,Q in H?? ||??(A + BQC) ??-1||??, where ?? is constrained to be block-diagonal. Existing methods addressing this problem require complete knowledge of the scaling functions ??. In this paper we provide an alternative algorithm which requires only the values of ?? at the unstable poles of the nominal plant. Determining the corresponding robust controller involves outer function interpolation and we provide here a new procedure for this problem. This procedure yields far lower order interpolants than previous methods. Also, we derive sufficient conditions for infinite stability margins for these problems.